The signing by Ukraine of the Association Agreement with the European Union will complicate the country's trade relations with the Customs Union, Ukraine's representative in the Eurasian Economic Commission, Viktor Suslov, has said.

"This, of course, will complicate our relations, and there's no doubt about it," he told Interfax-Ukraine on Thursday.

"We have to make a choice here. It's impossible to sign the association agreement with the European Union and maintain a liberal trade regime with the Customs Union. So we have to prepare for the fact that the Customs Union could gradually introduce the kind of methods of control that it uses in relation to the products of the European Union," Suslov said.